1. Field of the Invention
The instant invention pertains to flow-directed guidewires and catheters, and in particular, to flow-directed guidewires useful for traversing a stenosis in a blood vessel.
2. Discussion of Related Art
Despite advances in guidewire and catheter technology, high-grade stenoses in the coronary or peripheral vasculature continue to pose a considerable challenge. Even experienced interventionalists can expend significant time, effort and resources in crossing these lesions. Furthermore, multiple, failed attempts at traversing a lesion can increase the risk of distal embolization which may have significant implications in some vascular beds. Numerous modifications to guidewires have attempted to increase the efficiency of crossing stenotic areas. For example, hydrophilic coatings, varying degrees and lengths of “floppiness”, and different shapes on the wire tip have all been utilized to facilitate this process. The very existence of multiple products speaks to the lack of universal efficacy of any single design. The central issue is that the tip of the wire must enter the opening of the stenosis. This opening is usually eccentric and difficult to locate efficiently. In effect, trial and error is the current method of choice to get the tip of the wire into the stenosis and may involve multiple attempts. It is obvious that a guidewire that will quickly and atraumatically cross lesions will be of tremendous benefit to both the interventionalist and to the patient.
In addition to crossing lesions in peripheral vascular beds, endovascular technology is being increasingly applied to treat carotid artery lesions (Roubin et al). An integral step in this procedure is to gain wire-access to the appropriate carotid artery via the aortic arch and advance a sheath over this wire into the common carotid artery. The aortic arch anatomy can be very difficult to navigate and the aorta and carotid orifice can be heavily diseased. It has been established that distal embolization due to excessive instrumentation in the aortic arch can lead to cerebral events during carotid stenting procedures (Coggia et al, Macleod et al). Innumerable catheters have been developed to help engage the carotid or innominate orifice but this can be difficult, dangerous and time-consuming. Again, a device that will efficiently and safely allow a wire to be placed into a carotid artery would be useful to clinicians and beneficial to patients.
Flow-directed catheters have been available for decades. These catheters have found application in neuro-intervential radiology. In general they are simply very floppy or flexible tubes of small diameter which will small enough and flexible enough to be effected by fluid velocity and thus are directed through vessels into the branches with the highest flow. Multiple variations of this concept have been disclosed and claimed in the following U.S. patents: U.S. Pat. No. 6,524,299 (Tran et al.); U.S. Pat. No. 5,336,205 (Zenzen et al.); U.S. Pat. No. 5,538,512 (Zenzon et al.); U.S. Pat. No. 6,193,705 (Mortier et al.); U.S. Pat. No. 5,947,939 (Mortier et al.); U.S. Pat. No. 5,730,733 (Mortier et al.); U.S. Pat. No. 6,221,059 (Chiang et al.); U.S. Pat. No. 5,899,890 (Chiang et al.); U.S. Pat. No. 6,083,222 (Klein et al.); U.S. Pat. No. 4,983,169 (Furukawa); U.S. Pat. No. 5,499,973 (Saab); and U.S. Pat. No. 5,911,715 (Berg).
Inflated balloons have been conceived as a method to utilize the flow within a vessel to direct a catheter. In U.S. Pat. No. 4,029,104 (Kerber) an inflatable leaking balloon is described as a tool for using the flow in a vessel to direct the balloon in the direction of flow and also to provide a means of local drug delivery through the small holes in the balloon. Another example of a balloon catheter directed by flow is U.S. Pat. No. 4,024,873 (Antoshkiw et al.).
U.S. Pat. No. 5,906,618 (Larson) describes a catheter with a deployable parachute attached to the distal tip. The parachute may be guided by the flow within a vessel or by fluid injected through the catheter. A guidewire may be advanced through the lumen of the catheter to provide further direction of the catheter into a desired vessel branch. U.S. Pat. No. 6,491,671 (Larson et al.) describes a catheter with a catheter which is directed within a vessel by a wing shaped structure which provides hemodynamic lift in the presence of flow. This wing shaped structure is utilized to guide the tip of the catheter into a desired vessel branch.
U.S. Pat. No. 6,635,068 (Dubrul et al.) describes a catheter with an expandable wire mesh at the distal tip. The wire mesh may be expanded by the operator and flow within the vessel may direct the wire mesh and catheter. The wire mesh may also be used as an occlusion device.
In U.S. Pat. No. 6,726,700 (Levine) and U.S. Pat. No. 6,976,991 (Hebert et al.) describe a catheter with an inflatable balloon which may assist in guiding the catheter through tortuous vasculature. The catheter may include a flexible region where the tip of the catheter may be effectively steered by placing a bent wire within the catheter to bend the catheter in this flexible region so that by torquing the catheter with advancement it may be directed into a desired portion of a vessel such as an aneurysm.
Since 1991, flow-directed catheters have been commercially available. However, their use has been limited by the lack of ability to maneuver in tortuous vascular anatomy and cross stenoses. Typically, a guidewire is required to navigate these anatomic hurdles. The distinction is crucial as catheters are limited by size, structure, rigidity, floppiness or other properties in their design and are not useful for the aforementioned situations. The use of a wire with a floppy tip that can also exploit the flow-dynamics inherent to the vascular system will overcome these limitations